Intraocular lenses are routinely implanted in a patient's eye during cataract surgery to compensate for the lost optical power that results when the natural lens is removed. In other applications, an intraocular lens can be implanted in a patient's eye, which retains its natural lens, so as to provide an optical power for correcting a refractive error of the natural eye. Many different types of intraocular lenses exist for treating a variety of conditions to provide a patient with corrected vision.
Periodic diffractive structures can diffract light simultaneously into several directions, also typically known as diffraction orders. In multifocal intraocular lenses, for example, two diffraction orders can be utilized to provide a patient with two optical powers, one for distance vision and the other for near vision. Such diffractive intraocular lenses (“IOLs”) are typically designed to have an “add” power that provides a separation between the far focus and the near focus. In this manner, a diffractive intraocular lens can provide a patient in whose eye the lens is implanted with vision over a range of object distances. For example, a diffractive IOL can replace a patient's natural lens to provide the patient not only with a requisite optical power but also with some level of pseudo-accommodation. In another application, a diffractive IOL or other ophthalmic lens can provide the eye of a patient who suffers from presbyopia—a loss of accommodation of the natural lens—with pseudo-accommodative ability.
One example of a multifocal diffractive IOL is the ReSTOR apodized diffractive lens, manufactured by Alcon Laboratories, Inc., of Fort Worth, Tex. The ReSTOR lens is used to create two primary lens powers to provide a patient with good vision at different distances. It would be useful to (a) to measure the optical quality of such a diffractive lens in the laboratory or a manufacturing facility, and (b) to measure the optical quality of an eye that contains a diffractive lens (where the overall optical to performance is affected by properties of the eye).
Wavefront measurement systems are used in ophthalmology and other fields to measure an optical wavefront, but this is normally done for a lens with a single focus. These systems are not specifically designed to evaluate a lens with more than one power, and, in particular, they are not designed to evaluate diffractive lenses with more than one power.
There is therefore a need for a method and system for measuring the optical properties of a diffractive lens, such as by a wavefront analysis, both in a laboratory or manufacturing facility, and when implanted in an eye.